Impact wrench



May 23, 1950 c. E. FITCH 2,508,997

IMPACT WRENCH Filed Feb. 27, 1945 INVENTOR.

Patented May 23, 1950 FJUNITED rm-mew WRENCH Fitch, Bryan, ()hio; assignor jo The Aro Equipment Oorporatiom-Bryan, ()hio; a,

-Aiiialihatifiif Fbfiuary 27, 19%; Serial Nuts? 95913 Claims. I (01. 192 3045) My present Y invention relates toan imp-act'tool such as *one for driving wrench -=heads and the like, the mechanismthereof" being driven --by=-a pneumatie-motoror the' like.

impaet nlu'teh P connection between -amotor--and a wreneh or"similar tool; such connection being comparatively simple i-n construotiom and involving a minimum nuin-ber' 'of:--parts wh-i'clr are--in'- expensive to manufacture.

"Another obj ect is to'-piovide-an -impact clutch connection which -utilizes "centrifugal force 'to efiectan operative connection while" rotating a him bolt :or the like,-and-= upon -a -'predetermined resistance toturning torque-being offeredby the nutor'bolt; the mechanism automaticallychanges to an-impactoperatiomwherein'thehammer e1ement's'=--a1-ternate1ystrikeandre1ease=-;-anvil :elements to thereby secureatightening f the bolt or nutto the desireddegree.

-Sti1l another object is --toprovide a connection betweema'driving element andan -anvii element eonsisting of rollers or similarhammer elements or impact members-carried by the driving element and freely movableradially relative there- 't0,--theiroutward-andinward movements being 'hmited -withthe rollers-in position when-at their outer limits of movement te strike anvil-like projections' orabutments ot- -the anvfl element and thereafterbeing-releasedfrom'the -anvll likepro- :jeetions'byan inward-eam-ming-action between the projections and the rollers. I a

= A further ebjeet is'to provide animpact clutch connection utilizing rol-lersas hammer elements whichar'eatreely rotatable to'd-istributethe wear around them and which are-"limited in their: ra-

dial movements relative to-a; driving element so th-at-thevmaystop; rotation due to-frictionalengagernent with the limiting means and strike the anvil-likeprojections while they -are-not rota-t ing, thus eliminating a --c1irnbing-efieet of the rrollers on thecam surfaces of the anvil-like-proi t m, v Still a further Object is to provide a-modi fied form (if-structure which uses--slidably mounted m; nonrotatable hammer elements;

' With" these and other objects in vie'w jh'iy' invention consists "in the construction, arrange- 'ment and combination of-the' various parts of fifty device" whereby the objects-contemplated amattained, as hereinafter 'i'riore f hilly fet forth, minted out i'nhriy claim's arid 'illlis'trated in the accompanying drawings, wherein: g

I Fig. I is a side elevatiori o'f an paetraoremtoaymg'm'y '1'r'wefition, V themote and 'theweact'mechanismteing snewif m sseuse;

2 Fig; 2 is" a sectional view-on the line-jz of 1 ;=showing the cooperating partsofthe impac't'mechanism in impactingposition; r r

Fig. 3"'is-a"-similar-sectional view wherein the hainifier elements have been retracteddue to fur ther rotationof the-driving element; I

"Fig; 4-is a-- perspective view of the driving elementi and I V w FigsB is'a -sectional viewsimilarto Fig.- 3-sh6wing'a'modified construction. v

On -the accompanying drawing I have used the reference character to indicate, in general a 'motorsuoh'asone of thepneumatic type. The shaft of-the--motor=is--shown at l0-and constitutes the prime mover for theimpact mechanism and awrenehhead i2. 'Thew-renchhead 1s mountedon-a wrench shaft 16 having a squared "portion it cooperating with the socket-'like wrench head; torotate 1 the: head with the shaft. The shaft I6 is journaled in a bearing por ion of a housing Hiand has, onits innere'ndfa disk 22. The disk 22rnayhe' termed an anvil elementand has apair of anvi1 projections or abutments -26, The-housing it is secured to the motor M- and isadapted for housing-the anvil element and the wait-enemas between it and the shaft it, which will now be described.

driving element or carrier member is shown at23. This element is relatively heavy and serves somewhat asa fly wheel. It' is driven b'y th'e :motor shaft i8, as by being Tsplined thereto," as shown at 32, the splines Y being formed in a hub a t-of thedriving-element 28'. l The details of the motor are not shown-as it is the usual ty-pe'having arotor provided withradial 'slots' in which s-l-idahle -vanes reciprocate, the rotor being" eecentric-in relation to an outer casmg'pr the ma ton and suitable inletand exh'aust ports being provided in thausaal m nner. Motors-of this type" are incommon use for "operationhytfihipressedair at -pressiiies of s'evnty-five to'o'rie hundred and-twenty-five pounds per square inch, and'areparticularly satisfactory for ober-ation or an impact Wrench o f 'th'e kinddisclosed, alth h other types -and even electric inotors, hiay he found satisfactory. V

The driving ejieianttrt rner member 28 airther "has a harallel sided islet 4 3] therein h produces atop-wall 40 and a bottom wall 2 in which-impact-meihhers or hammer e1eme'i1ts4'6 are mounted with slight Ioosenss. These" jmnier' elirihfts; in the present instance-are in the rennet roller g M 'Eatih iollij' has, ifi'it's'i'efld, a iw le r di m e th n a themes '40" and "EZ of me amine e 3 has a pair of the pins 50 mounted therein as by a press fit. The pins 50 limit both the inward and the outward movements of the rollers 46 for an important purpose, which will hereinafter appear.

To serve as a means to prevent wobble of the lower end of the driving element or carrier member 28 in Fig. 4 it is provided with a perforation 52 in which a pilot pin 54 is mounted. The pilot pin 54 has a flange 56 surrounding it and a portion 58 received in a socket 611 of the anvil shaft 18.

Although having the hammer elements or impact members 46 comprising rollers whereby the wear is evenly distributed has its advantages, slidable but non-rotatable hammer elements or impact members may be provided as in Fig. 5. The parts in this figure corresponding to the previous figures bear the same reference numerals, with the addition of a. The hammer elements or impact members 46, it will be noted, are not round, but of such shape that they slidably fit the slot i l without possibility of their turning therein. The sockets 48*- for the limiting pins 50 are illustrated in the form of slots rather than enlarged openings. The impacting operation is substantially the same, with the edges of the anvil elements or abutments 26 and the cooperating edges of the hammer elements or impact members 46* suitably shaped so as to provide a camming action. Either the hammer element or the anvil element may have the cam surface formed thereon, or both of them may, as in Fig. 5, the prime consideration being that upon stalling of the motor the build-up of air pressure behind the vanes therein will tend to rotate the driving element 28*, and through the camming action eiiect inward movement of the hammer elements so that they pass the anvil elements.

Practical operation Assuming the parts in the position shown in Fig. 2, and rotation being in a clockwise direction, it will be obvious that rapid rotation of the driving element 28 will cause the rollers 46 to remain outward due to centrifugal force, and limited in their outward movement by the pins 50 being engaged by the inner edges of the socket 48. The anvil-like projections or abutments 26 have cam faces 21, two of which, it will be noted, are engaged by the rollers or hammer elements 45. This will cause a positive drive from the driving element 28 through the rollers 46 to the anvil member l6-2226 for rotating the wrench head l2 and thereby the bolt or nut while it is driven home" and until such time that its resistance to turning increases to such a point that the faces 21 will cam the rollers 46 inwardly against the action of centrifugal force. The inward camming action will force the rollers as to the position of Fig. 3, and in this position it will be noted that the rollers are limited against inward movement by the outer edges of the sockets 48 engaging the pins 50. This prevents them from striking each other, as would be caused by their momentum when thrown inwardly by the cam faces 21, and thus tipping of the roller surfaces is avoided. The pins 50, by limiting the outward movement of the rollers or hammer elements 46, make it unnecessary to provide an annular track carried by the anvil member for them to roll on, and has the further desirable effect of stopping the rotation of the rollers betweenimpact blows on the anvil-like projections or abutments 26. After the rollers pass the anvil elements in their rotation beyond the Fig. 3 position they are again thrown outwardly by centrifugal force, and the friction between the sockets of the rollers and the pins 50 stop them from rotating before they again strike the next succeeding anvil-like projections. Thus they do not have a tendency to roll up over the cam face 21, as would be the case if they were rotating because of having traveled on an annular track, and a more positive impact blow is delivered due to the type of coaction thus had.

It will be noted that the essential features of the invention are a driving element, a driven element and a driving connection between the two, which consists of hammer elements or impact members which are movable radially of the driving element. Accordingly, the hammer elements or impact members may normally remain outward by centrifugal force for causing simultaneous wrench rotation with motor rotation, and are cammecl inwardly by the cam faces of the anvil element after stalling occurs due to the resistance to turning by the bolt or nut. The centrifugal force of the hammer elements or impact members is suspended due to the stalling action, so that the cam faces 21 then effect their releasing action as the driving element 28 is urged to continue its rotation by the compressed air behind the blades of the motor M. After that, centrifugal force and acceleration of the motor operate to bring the hammer elements into proper position for delivering successive impact blows against the cam faces 21 as long as the tool continues to operate.

The arrangement disclosed is symmetrical about a plane through the axis of rotation so that rotation of the tool in either direction is possible with the desired impacting efiect for either tightening or loosening bolts and nuts. During the loosening operation, impact operation would occur until such time as the resistance to turning had decreased so that the rollers stay out by centrifugal force and positively rotate the bolt or nut until the motor is stopped. Compared with devices in the prior art, the structure herein disclosed is substantially simple from the standpoint of having but few parts, and those parts simple in construction so as to be inexpensive for renewal, while, at the same time, all mechanical complications of operation are minimized.

The driving element or carrier member 28 is comparatively easy to make because the slot-M therein requires only a breaching operation for its formation. By then having the pins 50 limit the rollers 45 against inward movement, the rollers are kept out of contact with each other, as would be the case if they were not so limited. This minimizes wear on the rollers and increases the life of the tool considerably.

Although I prefer to have the hammer elements or impact members 46 in the form of rollers, they may assume other shapes, as suggested in Fig. 5. A change of this character, and many others, may be made inthe construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modifled forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim as my invention:

1. An impact clutch of the character described comprising relatively rotatable driving and anvil members, the driving member having a slot therein, a pair of roller elements carried in said slot and movable by centrifugal force outwardly therein, means of coaction between said roller elements and said driving element for delivering a series of rotational hammer blows to said anvil member in the rotation of the driving element relative to the anvil member, said roller elements being retained in said slot of said driving element by means of recess and pin means at the opposite ends of said slot to limit their movement outwardly relative thereto.

2. An impact clutch comprising relatively rotatable anvil and driving elements, a pair of abutments on the anvil element, the driving element having a slot therethrough, rollers constituting hammer elements, said rollers being mounted in said slot and confined thereby to positions substantially parallel to the axis of rotation of said driving element, and coacting pins and sockets in said slot and said rollers to limit the inward and outward movement of the rollers, said rollers being movable in response to centrifugal force to their outer limits of movement for delivering a series of rotational blows to said abutments, said abutments effecting inward movement of said rollers after an impact blow has been delivered.

3. A reversely acting impact clutch comprising relatively rotatable anvil and driving elements, spaced striking surfaces on said anvil arranged in an orbital path about the driving element, said driving member having a cross-slot, hammer elements movable therein comprising rollers having movement radially of the driving element into and out of the path of the striking surfaces, said rollers delivering a series of rotational hammer blows to said striking surfaces in either direction of rotation of the driving element relative to the anvil, and means of coaction between said rollers and said driving element to limit the outward movement of the rollers to such path and the inward movement to positions out of contact with each other.

4. A reversely acting impact clutch comprising relatively rotatable anvil and driving elements, spaced striking surfaces on said anvil arranged in an orbital path about the driving element, said driving element having a cross-slot, roller-like hammer elements movable therein into and out of the path of the striking surfaces, said hammer elements delivering a series of rotational hammer blows to said striking surfaces in either direction of rotation of the driving element relative to the anvil element, and means of coaction between said rollers and said driving element to limit the outward movement of the rollers to such path.

5. A tool of the character described comprising a rotary driven element, a rotary driving element therefor, a hammer element carried by said driving element for inward and outward movement relative thereto, centrifugal force effecting such outward movement, means to limit the outward movement to a path where the hammer element will contact said anvil-like projection only, and means of cooperation between said projection and said hammer element to return the hammer element inwardly upon continued rotation of the driving element after the hammer element has struck said anvil-like projection with an impact blow.

6. A device for accumulating torsional force in an impact tool comprising a rotary driving element; an anvil coaxial with and spaced from said driving element; and a rotative connection between said driving element and said anvil comprising a carrier member disposed coaxially between said anvil and said driving element and connected with said driving element for rotation at the same rate as said driving element, an abutment projecting from said anvil outside only a part of the periphery of said driving element and formed with two lateral cam surfaces, a pair of impact members carried by said carrier member and movable only radially with respect thereto, and means provided on said impact members and said carrier member for confining said radial movement between outer points where said impact members will strike said cam surfaces on rotation of said carrier member and inner points where said impact members will clear the inside of said abutment, outward radial movement of said impact members being effected by centrifugal force and inward radial movement by resistance of the work against turning torque and consequent movement of said impact members over one of said cam surfaces.

CLIFFORD E. FITCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,874,658 Tschudi Aug. 30, 1932 2,326,347 Forss Aug. 10, 1943 2,373,664 Emery Apr. 17, 1945 2,425,793 Fosnot Aug. 19, 1947 2,439,337 Forss Apr. 6, 1948 FOREIGN PATENTS Number Country Date 318,623 Great Britain Dec. 3, 1930 

